Spatial-temporal variations and transport process of polycyclic aromatic hydrocarbons in Poyang Lake: Implication for dry–wet cycle impacts

Abstract

The dry-wet cycles of the lake-catchment system may affect the spatial-temporal variations and transport of specific volatile organic compounds. In this study, we analyzed 16 priority polycyclic aromatic hydrocarbons (PAHs) in water, suspended particulate matter (SPM), air, soil and sediment in the Poyang Lake, which is the largest freshwater lake in Southeast China. The samples were collected from intertidal zone of the Poyang Lake, in both the dry and wet seasons, corresponding to the exposure and submersion periods, respectively. Concentrations of target PAHs in air, water, SPM and sediments were 0.8–13.5 ng/m3, 5.1–62.0 ng/l, 117–4651 ng/g and 16.4–775 ng/g, respectively. Concentrations of PAHs in sediments were found to be significantly related to total organic carbon and water content (p < 0.01). Compared to the sediment samples, the low molecular weight (LMW) PAHs (2–3 rings) accounted for greater proportions in water, SPM and air. Results suggest that the occurrences of PAH species are affected by their lipophilic properties. Molecular diagnostic ratios of PAH isomers in multimedium indicated that PAH presence in the Poyang Lake were attributed to both pyrogenic and petrogenic sources, and source contributions in different medium were shown to vary. Sediment-water and soil-air exchanges showed that the sediment plays a role of secondary emission sources for most LMW PAHs, and some high molecular weight PAHs (e.g., BghiP, IcdP and DahA) had different transmission directions in the alternate process of exposure and submersion. These findings provide a better understand of migration mechanism among the air, water body (including water and SPM) and sediment PAHs driven by dry-wet cycles.